The invention relates to an internal-combustion engine having at least one piston/cylinder unit containing a combustion chamber, having an intake path leading into the combustion chamber, an exhaust gas path leading out of the combustion chamber and having an exhaust gas manifold, an exhaust gas recirculation path leading from the exhaust gas manifold into the intake path, and a cooling device for cooling the recirculated exhaust gas. The invention further relates to an exhaust gas manifold for such an internal-combustion engine.
An internal-combustion engine of the above-mentioned type is known, for example, from German patent document DE 100 11 954 A1. The cooling device for cooling the recirculated exhaust gas is formed by an exhaust gas heat exchanger, which is constructed as a component that is separate from the exhaust gas manifold and is fastened directly to the exhaust gas manifold. By means of a valve, a portion of the exhaust gas flow can be guided either through the exhaust gas heat exchanger into the exhaust gas recirculation pipe or directly into the exhaust gas recirculation pipe into the intake pipe or the intake path of the internal-combustion engine.
From German patent document DE 43 24 458 B4, a water-cooled exhaust gas manifold for an internal-combustion engine is known, which has a double-walled outer pipe, through which cooling liquid flows and which contains an exhaust-gas guiding inner pipe which is held in the outer pipe and, with the exception of fastening points, is thermally insulated from the outer pipe by an annular gap. By means of this cooled exhaust gas manifold, it is achieved that, when the internal-combustion engine is started, the exhaust gas is cooled only slightly so that a catalyst will rapidly reach its operating temperature. It is only in the upper temperature range, which considerably stresses the catalyst, that heat is withdrawn from the exhaust gas so that the catalyst will not be endangered by unacceptably high temperatures.
FIG. 3 of the present application illustrates an internal-combustion engine known per se, which has an intake path and an exhaust gas path.
The intake path for supplying the, in the illustrated example, four-cylinder internal-combustion engine 10 with fresh air or a fresh charge, which intake path as a whole has the reference number 8, leads from an air filter 12 through a charger turbine 14 of an exhaust gas turbocharger, then through a charge air cooler 16 and further through a throttle valve part 18 into an air intake plenum 20, which is connected by way of intake ports, respectively, with one of the piston cylinder units of the internal-combustion engine 10.
An exhaust gas path of the internal-combustion engine, which, as a whole, has the reference number 22, contains a double-flow exhaust gas manifold 24, from which the exhaust gas flows through the exhaust gas turbine 26 of the exhaust gas turbocharger, subsequently through a catalyst system 28 and finally through a muffler 30.
From the exhaust gas manifold 24, an exhaust gas recirculation pipe 32 leads through an exhaust gas recirculation cooler 34 and an exhaust gas recirculation valve 36 upstream of the air intake plenum 20 back into the intake path 8.
The valve opening area of the exhaust gas recirculation valve 36 is controlled in a manner known per se as a function of operating parameters of the internal-combustion engine.
The exhaust gas recirculation through the exhaust gas recirculation pipe 32, the exhaust gas recirculation cooler 34 and the exhaust gas recirculation valve 36 results in relatively high constructional expenditures, which require space and lead to additional components with corresponding additional mounting expenditures.
There is therefore needed an internal-combustion engine having a simplified construction of the exhaust gas recirculation system.
According to the invention, an internal-combustion engine having at least one piston/cylinder unit containing a combustion chamber, having an intake path leading into the combustion chamber, an exhaust gas path leading out of the combustion chamber, and having an exhaust gas manifold, an exhaust gas recirculation path leading from the exhaust gas manifold into the intake path, and a cooling device for cooling the recirculated exhaust gas, is provided. The cooling device for cooling the recirculated exhaust gas cools the exhaust gas manifold and the exhaust gas recirculation path branches off the cooled exhaust gas manifold.
In the case of the internal-combustion engine according to the invention, no individual cooling device or a cooling device constructed as a component to be mounted separately is required for cooling the recirculated cooling gas. On the contrary, the exhaust gas manifold cooled for protecting the catalyst system is also used for cooling the recirculated exhaust gas.
An exhaust gas manifold according to the invention contains a housing for the connection to the exhaust gas side of an internal-combustion engine. At least one exhaust gas duct is constructed in the housing, which exhaust gas duct can be connected to an exhaust gas duct of the internal-combustion engine and ends in at least one outlet opening connectable to an exhaust gas system of the internal-combustion engine. An exhaust gas recirculation duct, which originates from the exhaust gas duct and which ends in an exhaust gas recirculation opening, as well as a cooling device by which at least the exhaust gas flowing through the exhaust gas recirculation duct can be cooled, are provided.
Advantageous embodiments and further developments of the internal-combustion engine according to the invention as described herein.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.